A cardiac rhythm management (CRM) system can include an intravascularly delivered coronary sinus (CS) left ventricular (LV) lead connected to a pectorally or abdominally subcutaneously implanted electronics unit. The CS/LV lead can be introduced into the CS vessel via the right atrium (RA). The CS/LV lead can be positioned such that electrodes at or near the distal end of the CS lead can be located in the CS tributary great cardiac vein (GCV) in association with the LV myocardium. Electrostimulations delivered from such CS/LV electrodes can be used to capture the LV myocardium. Such electrostimulations can be used to provide cardiac resynchronization therapy (CRT) to adjust the LV contraction rate, to spatially coordinate the LV contraction (such as within the LV or with a desired synchronization with a right ventricular (RV) contraction), or both.
A lead can be held in place screwing in a tine into the heart wall to secure the lead at a desired location. Screwing in a tine is less easy to do within vasculature, such as the CS vessel, than within an atrial or ventricular heart chamber. A more convenient approach can be to provide a shape-memory characteristic to the lead body. For example, a CS/LV lead can be configured with a shape memory characteristic such that, after insertion, the CS/LV lead can relax to assume a gradual spiral. The gradual spiral shape memory characteristic can help mechanically bias the lead against the inner wall of the CS to help secure the lead at a desired location.
Movement or dislodgement of a CS/LV lead can cause unwanted electrostimulation of the phrenic nerve, rather than the desired electrostimulation of myocardial tissue to elicit a heart contraction. Phrenic nerve stimulation can cause a hiccup-like contraction of the patient's diaphragm, which can be annoying or discomforting. Moreover, if the desired myocardial electrostimulation becomes suboptimal or ineffective, the beneficial effects of CRT can similarly become suboptimal or ineffective.
Edwards et al. U.S. Patent Pub. No. 2005/0004611 is directed toward a system and method for detecting dislodgement of an implantable medical device, including generating a current signal within the body and measuring certain response voltages.
Bradley U.S. Pat. No. 6,490,486 is directed toward an implantable cardiac stimulation device and method that monitors displacement of an implanted lead, including using an impedance measurement measured using the lead over a cardiac cycle of the patient's heart.
Rosenberg et al. U.S. Patent Pub. No. 2011/0066203 is directed toward an electrode and lead stability indexes and stability maps based on localization system data, including measuring electrical potentials to determine acute and chronic stability of an electrode.
Levine et al. U.S. Patent Pub. No. 2010/0087891 is directed toward systems and method for diagnosing an implantable medical device, including detecting lead dislodgement based upon measured parameters.
Cho et al. U.S. Pat. No. 7,873,410 is directed toward an implantable medical device with electromechanical delay measurement for lead position or dislodgement and ventricular dyssynchrony detection.